MIND - Development of the Safety Case Knowledge Base about the Influence of Microbial Processes on Geological Disposal of Radioactive Wastes
Minna Vikman, Hanna Miettinen & Markus Olin (VTT)
17/11/2019 VTT – beyond the obvious
This project has received funding from the Euratom research and training
programme 2014 - 2018 under grant agreement No. 661880
17/11/2019 VTT – beyond the obvious
Microbes in final repositories
▪ Produce gas (methane, CO2)
▪ Produce corrosive components (e.g. sulphide, acetate)
▪ Enhance/participate corrosion process
▪ Produce metabolites that form complexants with
radionuclides
▪ Change geochemical environment in repository (e.g. pH)
▪ Change redox state of the radionuclides
▪ Can affect the performance of engineered barrier
materials
▪ Can influence the solubility, the sorption and the mobility
of radionuclides
Photo:
Posiva
What microbes need ?
17/11/2019 VTT – beyond the obvious 3
What microbes need?• Space to grow
• Water availability
• Major nutrients: C,H,N,O,P,S
• Minor nutrients: e.g Fe, Ca, Mg,
Mn…
• Available microbial energy:
results of oxidation and
reduction
• Certain environmental
conditions (pH, temperature
etc.)
What microbes need?• Space to grow
• Water availability
• Major nutrients: C,H,N,O,P,S
• Minor nutrients: e.g Fe, Ca, Mg,
Mn…
• Available microbial energy:
results of oxidation and
reduction
• Certain environmental
conditions (pH, temperature
etc.)
What can we do?• Restrict space: porosity >0.2
µm
• Lower water availability
• Limit supply of major and
minor nutrients (diffusion)
• Create extreme physico-
chemical conditions (high pH,
temperature etc.)
• Control microbial respiration to
limit unbeneficial microbes
Information about
microbial communities
needed
What can we do?• Restrict space: porosity >0.2
µm
• Lower water availability
• Limit supply of major and
minor nutrients (diffusion)
• Create extreme physico-
chemical conditions (high pH,
temperature etc.)
• Control microbial respiration to
limit unbeneficial microbes
Information about
microbial communities
needed
Development of the safety case knowledge base about the influence of microbial processes on geological disposal of radioactive wastes
(MIND) 2015-2019
▪ WP1: Low and
intermediate level wastes
▪ WP2: High level waste
and spent fuel
▪ WP3: Integration,
communication and
Dissemination
▪ WP4: Project
management
1. Swedish Nuclear Fuel and Waste
2. Management Co, SKB
3. Microbial Analytics Sweden AB, MICANS
4. Belgian Nuclear Research Centre, SCK•CEN
5. Helmholtz-Zentrum Dresden-Rossendorf e.V.,
HZDR
6. National Nuclear Laboratory Limited, NNL
7. Ecole Polytechinique Federale De Lausanne,
EPFL
8. Techniscka Univerzita, The Czech Rebublic
9. Centrum Vyzkumu REZ, The Czech Rebublic
10. University of Machester, UK
11. Universidad De Granada, Spain
12. TVO
13. Posiva
14. Geologian tutkimuskeskus
15. VTTThis project has received funding from the Euratom research and training
programme 2014 - 2018 under grant agreement No. 661880
17/11/2019 VTT – beyond the obvious
▪ Improve the geological safety case knowledge on:• microbial processes controlling radionuclide, chemical
and gas release from long-lived intermediate level
wastes containing organics
• the influence of microbial processes on high level
waste and spent fuel geological disposal
▪ Integrate, communicate and disseminate results
and conclusions from the above listed objectives to
the broad European community involved in
radioactive waste disposal
Objectives of MIND
This project has received funding from the Euratom research and training
programme 2014 - 2018 under grant agreement No. 661880
VTT’s objectives in MIND
17/11/2019 VTT – beyond the obvious
WP1
Gas generation from low
level maintenance waste
WP2
Microbial influence on
bentonite structure
Sulphide formation in deep
groundwaters
This project has received funding from the Euratom research and training
programme 2014 - 2018 under grant agreement No. 661880
Gas GenerationExperiment (GGE)
17/11/2019 VTT – beyond the obvious
Gas Generation Experiment (GGE)
▪ In situ large-scale experiment in Olkiluoto
repository operated by TVO
▪ 16 waste drums (200 L) were filled with LLW
maintenance waste, placed in a concrete box and
closed in the gas tight tank of acid proof steel (20
m3)
▪ The tank was filled with river water
▪ Temperature is maintained in the level of +8°C -
+11°C
▪ The proportion of concrete to cellulose in the GGE
(mass ratio 6.5) is lower than in the actual
repositories
17.11.2019 VTT – beyond the obvious 8
Aim: to study gas generation
from cellulose-containing LLW
under conditions
representative of the VLJ
repository
Aim: to study gas generation
from cellulose-containing LLW
under conditions
representative of the VLJ
repository
Why gas generation matters?
▪ Gaseous radionuclides (e.g. 14C) can be
transported to the biosphere in the form of
methane gas (14CH4)
▪ Development of overpressure in the repository
• Disruption of the engineered barrier system
(EBS)
• Increase groundwater flow rates
▪ Produced gas in the geosphere can enhance the
activity of microbial communities
Enhanced migration of radionuclides in
groundwater to the biosphere17.11.2019 VTT – beyond the obvious 9
Gas generation rates
are higher in ILW and
LLW repositories
compared to
HLW/spent fuel
repositories because
of
• Larger volumes of
metals
• Larges volumes of
organic materials.
Gas generation rates
are higher in ILW and
LLW repositories
compared to
HLW/spent fuel
repositories because
of
• Larger volumes of
metals
• Larges volumes of
organic materials.
This project has received funding from the Euratom research and training
programme 2014 - 2018 under grant agreement No. 661880
Gas generation in repository conditions
1. Biodegradation of organic materials:
C - - -> CO2, CH4, (H2)
2. Corrosion of metals in the waste and
packaging (drums)
Fe +2 H2O → Fe(OH)2 + H2
3. Radiolysis of water and some organic
molecules in the waste packages, generating
mainly hydrogen
LLW maintenance in
Finland
40% Cellulose/hemicellulose-
based
- e.g. cotton cloth and gloves,
paper, cardboard
60% Non-cellulose/hemicellulose
based
- PE, PVC items, latex gloves,
fire protection cloth (glass
fiber), electric components,
metal components,
polycarbonate cloth
LLW maintenance in
Finland
40% Cellulose/hemicellulose-
based
- e.g. cotton cloth and gloves,
paper, cardboard
60% Non-cellulose/hemicellulose
based
- PE, PVC items, latex gloves,
fire protection cloth (glass
fiber), electric components,
metal components,
polycarbonate cloth
This project has received funding from the Euratom research and training
programme 2014 - 2018 under grant agreement No. 661880
Main observations from GGE
▪ Cellulosic and hemicellulosic components in
LLW were converted to methane and carbon
dioxide as a successive action of a complex
microbial consortium
▪ Heteregenous chemical conditions (pH,
dissolved organic carbon)
→optimal niches for microbial activity
→gas generation started sooner than expected
▪ Alkaline conditions (concrete) neutralized sooner
than expected
• Production of CO2 and microbial metabolites
→ pH decreased close neutral
▪ Hydrogen was formed as a results of steel
corrosion (and during biodegradation of
maintenance waste) but was rapidly
consumed by microbes
Bentonite characteristics after TWO years storage with indigenous bentonite and water microbes17/11/2019 VTT – beyond the obvious
13
AIM:
To study if and how microbes and their metabolites
influence bentonite structure and performance in
bentonite-water-bedrock interfaces where bentonite
density and pressure is lower than planned for the
disposal facility
Bentonite Rock
Fracture
Background
14
Bentonite layers:
Silica
Aluminia
Silica
Fe3+
K+
K+
Fe2+
Fe2+
Fe2+
Fe3+
Fe3+
Na+
Ca2+
Microbial activity:
ferri- and sulphate
reducers,
other metabolites
Collapse of interlayers
in the presence of K+
Reduction/loss of
swelling
pressure
Mg2+
Interlayer with
exchangeable
cations and water
▪Will the bentonite swelling pressure be
reduced/lost in conditions favourable for
microorganisms
15
Anoxic and oxic bentonite (Wyoming type)storage experiment started 2016
ANOXIC:
Water mixture: 3 anaerobic ground-
waters + Olkiluoto surface water
(anoxic) 25:25:25:5 (mL)
Gas mixture: N2:CO2:H2 80:10:10
+ CH4 15 ml added after closure
Bottle volume 110 ml
Water 80 ml,
Rock crush 5 g,
Bentonite 5 g
Nutrients
OXIC:
Water mixture: Olkiluoto surface
water and anaerobic groundwater
mixture 65:5:5:5 (mL)
Gas mixture: Air
30°C 37°C
Nutrients: Na-acetate and -formate 0.1 mM, methanol 0.05 mM
Controls: 1) Abiotic: heat treated bentonite (180°C, 16h), sterile
filtered water, autoclaved rock
2) Bentonite microbes, sterile filtered water,
No nutrients
Some results and future plans
16
Hydrogen used within two weeks in anoxic bottle
Oxygen used in half a year in oxic bottles
Microbial activity low/decreased after one year
Microbial sulphate reduction ongoing in anoxic microbial
bottles by 35SO-label method, not in abiotic nor in oxic samples
No significant changes in bentonite structure in 2 years, microbes
are slow in nutrient poor environment
After 3 years: acceleration of microbes with nutrient addition
and next follow up after 4 years in KYT-2022 (Finnish
Researach Programme on Nuclear Waste Management)
Anoxic microbial microcosms Abiotic
Black
FeS
precipitate
Rock crush
Acknowledgement
▪ This study has received funding from
▪ The Euratom research and training programme 2015-2018 under
grant agreement No. 661880
▪ KYT2018, the Finnish Research Program on Nuclear Waste
Management
▪ Research team:
▪ Hanna Miettinen, Minna Vikman, Malin Bomberg, Mirva
Pyrhönen, Michal Matusewicz, Markus Olin, VTT
▪ Mohamed Merroun, University of Granada
THANK YOU FOR YOUR ATTENTION17
17/11/2019 VTT – beyond the obvious
▪ Vikman, M., Marjamaa, K., Itävaara, M., Nykyri, M., Small, J., Paaso, N., Microbial
degradation of low-level radioactive waste in repository conditions, Presentation,
Goldschmidt 2017, 13 - 18 August 2017, Paris, France 2017. European Association
of Geochemistry.
▪ Small, J., Nykyri, M., Vikman, M., Itävaara, M., Heikinheimo, L. 2017. The
biogeochemistry of gas generation from low-level nuclear waste: Modelling after 18
years study under in situ conditions, Applied Geochemistry. Elsevier. Vol. 84 (2017),
360-372. doi.org/10.1016/j.apgeochem.2017.07.012
▪ Vikman, M., Marjamaa, K.., Nykyri, M., Small, J., Miettinen, H., Heikinheimo, L.,
Haavisto, T., Itävaara, M. 2019. The biogeochemistry of gas generation from low-
level nuclear waste, Microbiological characterization during 18 years study under in
situ conditions, Applied Geogemistry 105, 55-67. 10.1016/j.apgeochem.2019.04.002
▪ Miettinen, H., Bomberg, M., Vikman, M. 2018. Acetate activates deep subsurface
fracture fluid microbial communities in Olkiluoto, Finland. Geosciences 8,
399. doi:10.3390/geosciences8110399
Publications and presentations
This project has received funding from the Euratom research and training
programme 2014 - 2018 under grant agreement No. 661880
